ABSTRACT
Natural oils and fats are liquids or semisolids consisting primarily of triacylglycerols (TAG). In literature, TAG are often referred to as triglycerides, even though this latter term is less accurate in representing the molecular structure of this class of compounds. The distinction between fats and oils is seen by their physical state at ambient temperature; the fats are solid and the oils are liquid. The two major sources of oils and fats are from animals and plants. Greater than 90% of commercial oils and fats used for human consumption are plant-derived vegetable oils. Unrefined natural oils and fats, after extraction from the source, comprise mostly TAG containing less than 5% of minor components such as sterols, phospholipids, tocopherols, fatty acids and partial glycerol esters. The minor components and their concentration in the crude oil depend upon the origin and method of oil extraction. The crude oils are subjected to various processing steps like degumming and alkali refining (to remove phospholipids and fatty acids), bleaching (to remove colored and polar matter) and steam stripping or deodorization (to remove volatile components) to make them suitable for human consumption. Oils subjected to these steps are usually referred to as RBD (refined, bleached and deodorized) oils and contain about 99% TAG.
